U.S. patent number 8,118,095 [Application Number 12/707,515] was granted by the patent office on 2012-02-21 for in situ combustion processes and configurations using injection and production wells.
This patent grant is currently assigned to ConocoPhillips Company. Invention is credited to Wayne Reid Dreher, Jr., Wendell P. Menard, Partha S. Sarathi, Thomas J. Wheeler.
United States Patent |
8,118,095 |
Sarathi , et al. |
February 21, 2012 |
In situ combustion processes and configurations using injection and
production wells
Abstract
Methods and systems relate to in situ combustion utilizing
configurations of injection and production wells to facilitate the
in situ combustion. The wells define vertically deviated lengths
that have different orientations from one another. Further, heating
processes such as resistive heating and cyclic steam stimulation
may take place in one or both of the injection and production wells
to precondition a reservoir prior to the in situ combustion.
Inventors: |
Sarathi; Partha S.
(Bartlesville, OK), Dreher, Jr.; Wayne Reid (Katy, TX),
Wheeler; Thomas J. (Houston, TX), Menard; Wendell P.
(Katy, TX) |
Assignee: |
ConocoPhillips Company
(Houston, TX)
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Family
ID: |
42558912 |
Appl.
No.: |
12/707,515 |
Filed: |
February 17, 2010 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20100206563 A1 |
Aug 19, 2010 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61153894 |
Feb 19, 2009 |
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Current U.S.
Class: |
166/260; 166/256;
166/302; 166/272.1 |
Current CPC
Class: |
E21B
43/305 (20130101); E21B 43/243 (20130101) |
Current International
Class: |
E21B
43/243 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bates; Zakiya W
Claims
The invention claimed is:
1. A method of conducting in situ combustion, comprising: forming
an injection well that extends in length deviated from vertical in
at least a first direction and at two locations having a vertical
offset from each other; forming a plurality of production wells
that each extend in length deviated from vertical with orientation
misaligned relative to the first direction, wherein at least one of
the production wells is deviated from vertical in a second
direction; injecting oxidant into the injection well to propagate
combustion; and recovering hydrocarbons through the production
wells.
2. The method according to claim 1, wherein the first direction is
misaligned relative to the second direction by an angle that is
between 20.degree. and 160.degree..
3. The method according to claim 1, wherein the first direction is
misaligned relative to the second direction by an angle that is
about 90.degree..
4. The method according to claim 3, wherein the injection and
production wells are each deviated from vertical by about
90.degree..
5. The method according to claim 1, wherein the injection and
production wells are each deviated from vertical by between
80.degree. and 90.degree..
6. The method according to claim 1, further comprising heating a
reservoir surrounding the injection well along a vertically
deviated section of the injection well, wherein the heating occurs
without igniting oil in the reservoir and with operations conducted
through the injection well.
7. The method according to claim 1, further comprising injecting
steam into a reservoir surrounding the injection well along a
vertically deviated section of the injection well prior to igniting
oil in the reservoir.
8. The method according to claim 1, further comprising heating a
reservoir surrounding the injection well along a vertically
deviated section of the injection well with a resistive heating
element.
9. The method according to claim 1, further comprising introducing
heat to an area surrounding at least one of the production wells
with operations conducted through the at least one of the
production wells.
10. The method according to claim 1, further comprising heating a
reservoir surrounding the injection and production wells along
vertically deviated sections of the production and injection wells,
wherein the heating occurs without igniting oil in the reservoir
and with operations conducted through the injection and production
wells.
11. The method according to claim 1, wherein the injecting oxidant
occurs along a longitudinal section of the injection well and the
longitudinal section is closer to toes of the production wells than
heels of the production wells, is closer to surface than the toes
of the production wells, and comes closest to the production wells
intermediately along the longitudinal section.
12. A method of conducting in situ combustion, comprising: forming
an injection well that extends in length deviated from vertical;
forming a production well that extends in length deviated from
vertical toward the injection well; heating a reservoir surrounding
the injection well along a section of the injection well where
vertically deviated, wherein the heating occurs without igniting
oil in the reservoir and with operations conducted through the
injection well; initiating the in situ combustion after heating the
reservoir, wherein the initiating includes injecting oxidant into
the injection well; and recovering hydrocarbons through the
production well.
13. The method according to claim 12, wherein the injection and
production wells deviate from vertical in respective first and
second directions misaligned relative to one another.
14. The method according to claim 12, wherein the injection and
production wells deviate from vertical between 80.degree. and
90.degree. and in respective first and second directions misaligned
between 80.degree. and 90.degree. relative to one another.
15. The method according to claim 12, further comprising
introducing heat to an area surrounding the production well with
operations conducted through the production well.
16. The method according to claim 12, further comprising
introducing heat to an area surrounding the production well with
operations conducted through the production well, wherein the
injection and production wells deviate from vertical in respective
first and second directions misaligned relative to one another.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
None
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
None
FIELD OF THE INVENTION
Embodiments of the invention relate to methods and systems for oil
recovery with in situ combustion.
BACKGROUND OF THE INVENTION
In situ combustion offers one approach for recovering oil from
reservoirs in certain geologic formations. With in situ combustion,
an oxidant injected through an injection well into the reservoir
reacts with some of the oil to propagate a combustion front through
the reservoir. This process heats the oil ahead of the combustion
front. Further, the injection gas and combustion gasses drive the
oil that is heated toward an adjacent production well.
Success of the in situ combustion in a heavy oil or bitumen
environment depends on stability of the combustion front and
ability to ensure that oxidation occurring is an exothermic
reaction. Amount of beneficial thermal cracking of the oil to make
the oil lighter tends to increase with higher temperatures from the
oxidation. Further, oxidation of the oil by an endothermic reaction
can create hydrogen bonding and result in undesired increases in
viscosity of the oil.
Various factors attributed to failure of the in situ combustion
include loss of ignition, lack of control, and inadequate reservoir
characterization. For maximum recovery of the oil, the combustion
front must be able to stay ignited in order to sweep across the
entire reservoir. Due to issues such as formation heterogeneity
influencing the combustion front, prior approaches often result in
instability of the combustion front, premature extinguishing of the
combustion front, or inability to achieve or maintain desired
temperatures.
Therefore, a need exists for improved methods and systems for oil
recovery with in situ combustion.
SUMMARY OF THE INVENTION
In one embodiment, a method of conducting in situ combustion
includes forming an injection well that extends in length deviated
from vertical in at least a first direction and at two locations
having a vertical offset from each other. The method further
includes forming a plurality of production wells that each extend
in length deviated from vertical with orientation misaligned
relative to the first direction and at least one of the production
wells deviated from vertical in a second direction. Injecting
oxidant into the injection well to propagate combustion enables
recovering hydrocarbons through the production wells.
According to one embodiment, a method of conducting in situ
combustion includes forming an injection well that extends in
length deviated from vertical and forming a production well that
extends in length deviated from vertical toward the injection well.
Heating a reservoir surrounding the injection well along a section
of the injection well where vertically deviated occurs without
igniting oil in the reservoir and with operations conducted through
the injection well. Further, the method includes initiating the in
situ combustion after heating the reservoir and recovering
hydrocarbons through the production well. The initiating includes
injecting oxidant into the injection well and may be achieved
spontaneously or by using an ignition device.
For one embodiment, a method of conducting in situ combustion
includes injecting oxidant into an injection well to propagate
combustion and recovering hydrocarbons through a plurality of
production wells. The production wells define heels at where the
production wells turns toward horizontal and toes at where the
production wells terminates distal to the heels. The injecting
oxidant occurs along longitudinal sections of the injection well
that are closer to the toes of the production wells than the heels
of the production wells, are spaced from one another closer to
surface than the toes of the production wells, and come closest to
the production wells intermediately along the longitudinal
sections.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention, together with further advantages thereof, may best
be understood by reference to the following description taken in
conjunction with the accompanying drawings.
FIG. 1 is a three dimensional schematic of injection and production
wells in a formation, according to one embodiment of the
invention.
FIG. 2 is a schematic top view of the injection and production
wells shown in FIG. 1, according to one embodiment of the
invention.
FIG. 3 is a three dimensional schematic of a multilateral injection
well and dual production wells in a formation, according to one
embodiment of the invention.
FIG. 4 is a schematic sectional side view of the injection and
production wells shown in FIG. 3, according to one embodiment of
the invention.
FIG. 5 is a three dimensional schematic of heated horizontal
injection and production wells in a formation, according to one
embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the invention relate to in situ combustion.
Configurations of injection and production wells facilitate the in
situ combustion. The wells define vertically deviated lengths that
have different orientations from one another. Further, heating
processes such as resistive heating and cyclic steam stimulation
may take place in one or both of the injection and production wells
to precondition a reservoir prior to the in situ combustion.
FIGS. 1 and 2 illustrate an injection well 100 and a production
well 102 disposed in a formation 104. Vertical from a surface 105
of earth is represented in a "y" direction with "x" and "z"
directions being orthogonal to each other and the y-direction. For
some embodiments, the injection well 100 includes a horizontal
injector portion 106 that may extend lengthwise in the z-direction.
Further, the production well 102 may include a horizontal producer
portion 108 that may extend lengthwise in the x-direction.
Direction of deviation from vertical for the horizontal injector
portion 106 relative to direction of deviation from vertical for
the horizontal producer portion 108 defines an angle .theta.. While
the angle .theta. is shown to be about 90.degree., the angle may be
between 20.degree. and 160.degree., such as between 80.degree. and
100.degree.. For example, the horizontal producer portion 108 may
extend in the x-direction while the horizontal injector portion 106
may extend in orientation midway between the x-direction and the
z-direction creating the angle .theta. of 45.degree..
Further, angle of deviation from the y-direction for the horizontal
injector portion 106 and/or the horizontal producer portion 108 may
be between 20.degree. and 160.degree., between 80.degree. and
100.degree., or about 90.degree.. The angle of deviation from the
y-direction defines slant toward horizontal corresponding to
90.degree.. In comparison to exemplary less horizontally oriented
slanting shown in FIGS. 3 and 4, both the horizontal injector
portion 106 and the horizontal producer portion 108 deviate from
the y-direction by about 90.degree..
The production well 102 defines a heel 110 at where the production
well 102 turns toward horizontal and a toe 112 at where the
horizontal producer portion 108 terminates distal to the heel 110.
In some embodiments, the horizontal injector portion 106 is closer
to the toe 112 of the production well 102 than the heel 110 of the
production well 102. In operation, oxidant 114 injected into the
formation 104 along the horizontal injector portion 106 propagates
a combustion front 116 from the toe 112 of the production well 102
to the heel 110 of the production well 102. Examples of the oxidant
106 include oxygen or oxygen-containing gas mixtures. Injection of
the oxidant occurs at multiple spaced locations or continuous along
the horizontal injector portion 106.
For some embodiments, the horizontal injector portion 106 is closer
to the surface 105 than the toe 112 of the production well 102. The
toe 112 of the production well 102 may terminate prior to reaching
beneath the horizontal injector portion 106 or may extend beneath
the horizontal injector portion 106 such that the horizontal
injector portion 106 and the horizontal producer portion 108 cross
one another, spaced one on top of another. As the combustion front
116 progresses through the formation 104, combustion gasses (e.g.,
CO.sub.2 and CO) and hydrocarbons 118 warmed by the in situ
combustion drain downward by gravity into the horizontal producer
portion 108 and are recovered via the production well 102.
In some embodiments, the injection well 100 comes closest to the
production well 102 intermediately along the horizontal injector
portion 106 and may come within 5 to 30 meters of the production
well 102. Fluid communication exists between the horizontal
injector portion 106 and the toe 112 of the production well 102
upon initiating the in situ combustion. Spacing between the
horizontal injector portion 106 and the toe 112 of the production
well 102 enables this communication that is necessary for the in
situ combustion to progress through the formation 104. Further, the
horizontal injector portion 106 increases potential area for the
communication relative to utilizing only vertical injection wells
where lateral area for establishing communication is limited.
Location of entry for the hydrocarbons 118 into the horizontal
producer portion 108 changes along the horizontal producer portion
108 as the combustion front 116 moves through the formation 104.
After the combustion front 116 passes over part of the horizontal
producer portion 108, oil no longer flows into the part of the
horizontal producer portion 108 that is disposed behind the
combustion front and in clean sands devoid of oil. Inflow of the
hydrocarbons 118 ahead of the combustion front 116 toward the heel
110 of the production well 102 is limited to a region of mobile oil
caused by the in situ combustion.
Pressure from the injection and the combustion gasses act to drive
the mobile oil down toward the horizontal producer portion 108.
Existence of differential pressures from the injection and the
combustion gasses relative to inside the production well 102
augments gravity drainage into the production well 102. The
horizontal injector portion 106 and the horizontal producer portion
108 orientation relative to one another ensures that the combustion
front 116 remains stable and allows draining of the hydrocarbons
118 into the production well 102 without significant bypassing of
the mobile oil below the production well 102.
With the horizontal injector portion 106, injection is not limited
to any finite reservoir thickness in the formation 104 since areal
coverage can extend laterally. Lateral extent of the areal coverage
creates the pressure gradient discussed herein across the
combustion front 116 without loss of the gradient along the
z-direction of the combustion front 116. Quantity of the oxidant
114 able to be injected into the formation 104 corresponds to
available outlets into the formation that due to the horizontal
injector portion 106 are also not limited by any finite reservoir
thickness. The horizontal injector portion 106 thereby permits
sufficient rate of oxidant injection into the formation 104 to
result in high temperature oxidation or exothermic reactions during
the in situ combustion. Given that increase in oxidant supply tends
to raise temperatures for the in situ combustion, the rate of
oxidant injection possible through the horizontal injector portion
106 thus also enables thermally upgrading the mobile oil while in
the formation 104 to lighter oil.
Further, the areal coverage provided by the horizontal injector
portion 106 ensures sweep efficiency for the combustion front 116
across the formation 104. Heterogeneities in the formation 104 such
as an impermeable body 120 can result in gas channeling or
otherwise influence transmission of the oxidant 114 through the
formation 104. Any composition of relatively lower porosity within
the formation 104 may provide the impermeable body 120. The
horizontal injector portion 106 provides the oxidant 114 on
multiple sides of the impermeable body 120 that could otherwise
inhibit the oxidant reaching the combustion front 116 beyond one of
the sides of the impermeable body 120. In this manner, the
horizontal injector portion 106 mitigates change to the combustion
front 116 due to the impermeable body 120.
FIGS. 3 and 4 show a multilateral injection well 300 and first and
second production wells 301, 302 in a formation 304. Configurations
illustrated for the wells 300, 301, 302 exemplify suitable
variations of foregoing described aspects. Selection of appropriate
variations depends on reservoir particulars, such as size and
shape, within the formation 304. The injection well 300 defines a
first lateral wellbore 306 and a second lateral wellbore 307. The
first and second production wells 301, 302 have respective first
and second horizontal portions 308, 309 deviated about 90.degree.
from vertical. Drilling techniques employed to create any of the
wells 300, 301, 302 can create fish-bone patterns, multilaterals,
slant wells, or horizontal wells deviated about 90.degree. from
vertical.
The first and second production wells 301, 302 both recover
hydrocarbons during the in situ combustion generated by oxidant
injection through the injection well 300. Some embodiments include
additional production wells and/or injection wells. Regardless of a
production well to injection well ratio, at least one production
and injection well pair defines a configuration as set forth
herein.
Referring to FIG. 4, the deviation from vertical (the y-direction)
for the first and second lateral wellbores 306, 307 is less than
90.degree.. The lateral wellbores 306, 307 thus slant downward
while extending lengthwise in the z-direction. The first lateral
wellbore 306 permits injecting into the formation 304 above the
second lateral wellbore 307. Relative to using the second lateral
wellbore 307 alone, the first lateral wellbore 306 increases areal
coverage in the y-direction in addition to the z-direction and also
increases surface area available for injection.
Further, the first and second horizontal portions 308, 309 extend
lengthwise in an offset direction from the x-direction. With
reference to the angle .theta. shown in FIG. 2, misalignment
between the offset direction, in which the production wells 301,
302 extend in length deviated from vertical, and the z-direction,
in which the injection well 300 extends lengthwise deviated from
vertical, defines an angle of less than 90.degree..
FIG. 5 shows a heated horizontal injection well 500 and a heated
horizontal production well 502 in a formation 504. Only one of the
injection well 500 or the production well 502 may be heated for
some embodiments. Further, the heated horizontal injection well 500
and/or the heated horizontal production well 502 provide exemplary
heating of the formation 504 prior to conducting the in situ
combustion as may occur with any embodiments described herein.
Start-up represents a potential problem for the in situ combustion
since inefficient ignition processes due to lack of adequate
initial communication between the injection well 500 and the
production well 502 can promote endothermic reactions instead of
the exothermic reactions. When cold, bitumen in the formation 504
tends to block the communication between the injection well 500 and
the production well 502. Heating the formation 504 around a
vertically deviated section 506 of the injection well 500 and/or a
vertically deviated section 508 of the production well 502 reduces
viscosity of the bitumen and makes the bitumen mobile.
This reduction in viscosity results in decrease of initial oil
saturation around the injection well 500. In addition, the
reduction in viscosity allows for the combustion gasses and the
mobile oil to be produced through the production well 502. Heating
the deviated sections 506, 508 of the wells 500, 502 enables
heating of a lateral portion of the formation 504. Ability to heat
the lateral potion of the formation increases heating efficiency
and increases areal extent of the bitumen capable of being heated
to establish communication as desired. Since the communication
depends on proximity of the injection well 500 to the production
well 502, the heating further permits greater separation of the
injection well 500 from the production well 502.
In some embodiments, a conductive element 550 conveys current (i)
to resistive heating elements 551 disposed along the vertically
deviated section 506 of the injection well 500. The heating
elements 551 heat the formation 504 by thermal conduction. Heating
of the formation with the resistive heating elements 551 may take
place over an extended period of time, such as at least 100 days or
at least 300 days.
Cyclic steam stimulation provides another option for heating the
reservoir 504 surrounding the vertically deviated section 506 of
the injection well 500. While both the steam stimulation and the
heating with the elements 551 are depicted, one or both such
techniques may be utilized prior to the in situ combustion. For the
steam stimulation, a steam generator 552 converts a water input 554
into steam. An injector output 556 from the steam generator 552
directs the steam through the injection well 500 into the formation
504, where the steam is held in place to allow for heat of the
steam to transfer into the cold bitumen. Once this initial heat
transfer takes place, additional steam is injected into the
injection well 500. This process of injecting steam is repeated as
necessary to heat the formation around the vertically deviated
section 506 of the injection well 500.
Similar to the injection well 500, heating of the vertically
deviated section 508 of the production well 502 may utilize
resistive based elements 560 and/or the cyclic steam stimulation.
The resistive based elements 560 may be disposed only proximate a
toe 512 of the production well 502 where possible to heat the
bitumen between the injection well 500 and the production well 502.
A producer output 558 of the steam generator 552 may repeatedly
introduce steam pulses into the production well 502 for preheating
the formation 504 prior to performing the in situ combustion.
For some embodiments, the in situ combustion described herein may
take place after processes for steam assisted gravity drainage
(SAGD). For example, injecting steam into the injection well 100
shown in FIG. 1 may heat and drive oil into the production well 102
where the oil is recovered. Once recovery of the oil using this
steam injection diminishes beyond economical returns, the in situ
combustion commences as a follow-up recovery operation.
The preferred embodiment of the present invention has been
disclosed and illustrated. However, the invention is intended to be
as broad as defined in the claims below. Those skilled in the art
may be able to study the preferred embodiments and identify other
ways to practice the invention that are not exactly as described
herein. It is the intent of the inventors that variations and
equivalents of the invention are within the scope of the claims
below and the description, abstract and drawings are not to be used
to limit the scope of the invention.
* * * * *